Prosthetic implant failure mechanisms are numerous. Among the most prevalent causes of failure are polyethylene wear, loosening, infection, and mal-alignment. Polyethylene wear comprises the largest single identifiable cause of implant failure today. Moreover, polyethylene wear can predispose implants to loosening as a result of increased loading of the reformed tissues. As implant technology evolves, new and more complex modes of wear, damage, and failure are being identified. As a consequence of these facts, there is a great need for rigorous implant life cycle testing in simulator machines that are capable of replicating the subtleties of human motion.
Simulator machines address the implant longevity problem by providing a non-human environment in which new and existing prosthetic devices are evaluated using accelerated life testing. These machines allow researchers to isolate and study design deficiencies, identify and correct materials problems, and ultimately provide physicians and patients with longer life prosthetic systems. Simulator machines approximate human joint motion. Clearly, the closer the approximations of human joint motion, the more reliable are the results.